Saudi authorities have arrested ten more suspects in an alleged Iranian spy ring unveiled two months ago, according to an interior ministry spokesperson.

The eight Saudis, a Lebanese and a Turk bring the number of people arrested to 28, the official SPA news agency quoted the spokesperson as saying on Tuesday.

A Lebanese arrested in March has since been released.

"The results of investigations by security services have led to the arrest of the other ten involved in spying for this cell," the spokesperson said.

On March 19, the interior ministry said authorities had arrested 16 Saudis, an Iranian and a Lebanese in four regions, including the oil-rich Eastern Province, where Saudi Arabia's Shia Muslim minority is concentrated.

Shia-dominated Iran has denied any involvement in the alleged spy ring.

Saudi Arabia's conservative Sunni Muslim rulers have strained ties with Iran, which deteriorated further after a Saudi-led military intervention crushed Shia-led pro-democracy protests in neighbouring Bahrain in early 2011.